References of "Letawe, Yannick"
     in
Bookmark and Share    
Full Text
See detailThe Power of Deconvolution for Study of QSO Host Galaxies
Letawe, Géraldine ULg; Letawe, Yannick; Magain, Pierre ULg

in Proceedings of the International Astronomical Union, IAU Symposium (2010, May 01), Vol 267

The major challenge in studying QSO host galaxies is to remove the QSO contribution, which often outshines the whole system. Our group has acquired the technical ability to handle such data, for images ... [more ▼]

The major challenge in studying QSO host galaxies is to remove the QSO contribution, which often outshines the whole system. Our group has acquired the technical ability to handle such data, for images and slit spectroscopy, as well as integral field spectroscopy. We review here the major techniques developed by our team, and their latest applications. We are open for collaboration with other teams to spread the use of these powerful techniques. [less ▲]

Detailed reference viewed: 11 (4 ULg)
Full Text
See detailStudy of quasar host galaxies combining HST/ACS images and VLT Spectroscopy
Letawe, Yannick; Letawe, Géraldine ULg; Magain, Pierre ULg

in Macchetto, F. D. (Ed.) The Impact of HST on European Astronomy (2010, March 22)

We present the results of a study of the host galaxies of a few bright low redshift quasars, based on a combination of high resolution HST/ACS images with deep VLT spectra. Using a version of the MCS ... [more ▼]

We present the results of a study of the host galaxies of a few bright low redshift quasars, based on a combination of high resolution HST/ACS images with deep VLT spectra. Using a version of the MCS deconvolution algorithm specially adapted to HST images, the light from the central point source can be efficiently removed, which allows to study the environment of the quasar down to a few hundreds of parsecs from the center. In a similar way, the spectra can be separated into a quasar contribution and a spatialy resolved slit spectrum of the host galaxy. Combinig the images and spectra allows to carry out a detailed analysis of the immediate environment of the quasar: excitation and ionisation state of the gas, dynamics... Up to now, this method has been applied to six quasars, including the peculiar HE0450-2958 for which no host galaxy could be detected. [less ▲]

Detailed reference viewed: 29 (5 ULg)
Full Text
Peer Reviewed
See detailStudy of a homogeneous QSO sample: relations between the QSO and its host galaxy
Letawe, Yannick; Letawe, Géraldine ULg; Magain, Pierre ULg

in Monthly Notices of the Royal Astronomical Society (2010), 403(4), 2088-2104

ABSTRACT We analyse a sample of 69 quasi-stellar objects (QSOs) which have been randomly selected in a complete sample of 104 QSOs (R < 18,0.142 < z < 0.198, d< 10°). 60 have been observed with the NTT ... [more ▼]

ABSTRACT We analyse a sample of 69 quasi-stellar objects (QSOs) which have been randomly selected in a complete sample of 104 QSOs (R < 18,0.142 < z < 0.198, d< 10°). 60 have been observed with the NTT/SUSI2 at La Silla, through two filters in the optical band (WB 655 and V 812), and the remaining nine are taken from archive data bases. The filter V 812 contains the redshifted Hβ and forbidden [OIII] emission lines, while WB 655 covers a spectral region devoid of emission lines, thus measuring the QSO and stellar continua. The contributions of the QSO and the host are separated thanks to the MCS deconvolution algorithm, allowing a morphological classification of the host, and the computation of several parameters such as the host and nucleus absolute V magnitude, distance between the luminosity centre of the host and the QSO and colour of the host and nucleus. We define a new asymmetry coefficient, independent of any galaxy models and well suited for QSO host studies. The main results from this study are (i) 25 per cent of the total number of QSO hosts are spirals, 51 per cent are ellipticals and 60 per cent show signs of interaction, (ii) highly asymmetric systems tend to have a higher gas ionization level and (iii) elliptical hosts contain a substantial amount of ionized gas and some show off-nuclear activity. These results agree with hierarchical models merger driven evolution. [less ▲]

Detailed reference viewed: 24 (7 ULg)
Full Text
Peer Reviewed
See detailHigh precision photometry in crowded stellar fields
Magain, Pierre ULg; Courbin, Frédéric; Gillon, Michaël ULg et al

in SPIE Newsroom (2006)

A deconvolution-based method which allows to derive high-precision photometry of stars in crowded fields, proves very useful for a variety of astronomical projects, including transit searches for ... [more ▼]

A deconvolution-based method which allows to derive high-precision photometry of stars in crowded fields, proves very useful for a variety of astronomical projects, including transit searches for extrasolar planets. [less ▲]

Detailed reference viewed: 25 (3 ULg)